In the theatre banquet room kitchen half of which I built, they had granite tops all thru the dining room. And they wanted matching granite for the 48" passthru. I advised against it, they insisted. No heat lamp.
When doing a dinner, I'd preheat plates, plate and place on the pass. The plate was cold in 2 minutes. A towel underneath didnt help much.
Someone above suggested preheating the granite...
seriously have you ever tried to do that?
Granite is gorgeous and very tough, but beyond that it leaves a lot desired, and its over priced. I dont want it in my personal kitchen, I currently have premium porcelain 18 inch tile. And it doesnt cool plates like that. My other favorite being hardwood butcher block.
As to the cooling problem. I agree, start using insulated chargers under the plates. The only problem being, the plates cant be too hot, or they'll flark up the chargers.